The four important characteristics that define a perfectly competitive market are: Multiple Choice standardized good, full information, no transactions costs, participants are price takers. standardized information, finished good, no transactions costs, participants are price makers. standardized good, same information for buyer and seller, low transactions costs, participants are price takers. standardized good, full information, no transactions costs, participants are price makers.

Perfectly competitive markets are theoretical, because even commodities' markets (e.g. corn, oil, etc.) do not comply 100% with all the characteristics of a perfectly competitive market, but are close enough to consider them as such.

The 5 characteristics of perfectly competitive markets are:

Many participants (many buyers and sellers)
Standardized goods or services
Zero transaction costs
No barriers to entry
All participants can access perfect information

As I said before, no market complies 100% with these requirements, but some commodities' markets get close enough, but even there:

commodity traders charge a transaction fee
capital is a great barrier to entry that cannot be eliminated, e.g. it costs millions to drill and sell oil
not all participants will be able to access perfect information